What I hate most about continuity is when people are stupid about it and use it as a crutch to complain about how confusing comics are.
For example, someone posted, "This issue of FF where they meet the Beatles, is that in continuity?"
Answer : It doesn't matter. There is nothing in that issue that has an impact in a current issue of the FF.
Now if people want to complain about Black Cat meeting Carnage during Maximum Carnage and then they redid her first meeting in ... I forget which comic. I can respect that complaint, because that is the poor quality control there. But it doesn't really affect but one page of that comic.
But too often, continuity complaints are moronic.